Trying to decide on turbo size

[snakeraper11b]

The motor is going to be a 5.1 stroker 10:1, fox lake CNC head port, 226-220ish duration cams with an HPP twin turbo kit. I want a street tune with around 650-700 hp @ 15 psi +/1 psi, and the ability to go to 850rwhp for standing mile runs. I've decided on Precision Billet CEA 5558 journal bearing with the 55mm Anti-Surge S compressor housing - 4"in/2.5"out, 58mm turbine T3 v band exhaust housing. I cant decide on the .48 AR or .63 though. I cant find any compressor maps on this turbo either. Seeing as how the base configuration on most twin kits are t3/t4 50mm turbos I'm pretty sure this will be fine, just looking for insight from personal experience.

 

[snakeraper11b]

Leaning towards the 55mm .48 A/R even more. Just saw a dyno of a stock long block 03 make 830rwhp on twin 50mm crap turbos with .43 A/R @ 22 psi. Looks like the 55's will be good for high 900 rwhp #'s.

 

[TwinTurbo4vGT]

go a little bigger, like 57mm. I had twin 57s and they netted me 867rwhp when i had them.

 

[snakeraper11b]

go a little bigger, like 57mm. I had twin 57s and they netted me 867rwhp when i had them.

How much boost were you on? Dyno sheet? Also do you know the specs of the turbo?

 

[TwinTurbo4vGT]

How much boost were you on? Dyno sheet? Also do you know the specs of the turbo?

they were 57mm garretts. it was on 21lbs. Ill see if i can dig up the sheet, it was like a year and a half ago lol.

 

[RussZTT]

Go with their 61mm's. I put down little over 700rwhp on my 61's at 15psi.

 

[snakeraper11b]

Go with their 61mm's. I put down little over 700rwhp on my 61's at 15psi.

I wont be going over 57's at the very most. I feel like a well planned 55-57mm billet wheel twin with a 5.1 @ moderate compression will yield about the same, if not better power, while spooling quicker. I'm just really looking for someone who has had a similar set up to chime in with their experience.

 

[8URZ-28]

I agree. I saw a twin 57mm cobra in action one night and it really got my attention. I think Ive decided on a twin 50-57mm Billet kit for my build. Im coming from a twin screw and having a hard time giving up that low end grunt. Seems the smaller twins spool very quick and are perfect for a decent street setup.

 

[InvisibleBlade]

go a little bigger, like 57mm. I had twin 57s and they netted me 867rwhp when i had them.

Is that about maxing out the 57's?

 

[Turbo98]

Mid 800's on these cars is max for a 57mm turbo. That is really pushing that turbo hard though. The "50mm" turbos are actually 50 TRIM. The compressor wheel on those is actually 54mm. I've seen the twin 54's support 800rwhp or so. They are an efficient little turbo.

How much HP does Precision rate the 5558's at? The set-up doesn't matter a whole lot as far as peak power. Yes, it will make some difference though as it will put you at a differen spot on theh compressor map. But it could make less power too depending on where it lands. You won't find a compressor map as Precision does not have these.

I had 5857's on my car which has the 5.3L. It made 1028rwhp/1094rwtq but they were MAXED out. The car made ridiculous midrange power--885 ft-lbs tq at 4000 RPM's. They spooled fast too. I had .63 a/r housings.

For most of where you want to be power-wise (650-700), I think the turbos you spec'd would be perfect. Will they make 850rwhp? Maybe, maybe not. If they do, you'll be pushing them hard and creating a lot of back pressure. On top of that, the .48 housing will spool them fast but I doubt they will allow the 850 you're looking for. They'll choke off pretty quick. I didn't think Precision even offered the .48 housings anymore?